The present invention is related to a method for the preparation of copper (meth)acryloyloxyethyl phosphate coordination complex, which is useful for cutting off light in the near infrared region, and in particular to a method for the preparation of copper (meth)acryloyloxyethyl phosphate coordination complex by using water as a solvent.
PCT application WO 99/26951 (1999) discloses a copper (meth)acryloyloxyethyl phosphate coordination complex having the formula (I), which can be used to form an optical filter film for cutting off near-IR ray, or as a near-IR-absorbing agent in a coating composition:
R3xe2x88x92nPO(O31 )nCu(II)xe2x80x83xe2x80x83(I)
wherein R is CH2xe2x95x90C(CH3)COOCH2CH2O, and n is 1 or 2. This complex is synthesized by reacting a mixture of H3PO4 mono- and di-ester of 2-hydroxyethyl (meth)acrylate having the formula (II) with Cu acetate monohydrate having the following formula (III) in an organic solvent of methyl ethyl ketone as shown in the following reaction: 
wherein R and n are defined as above. This synthesis method uses an organic solvent detrimental to the environment and the operator, however.
The present invention provides a synthesis method for the complex having the above formula (I) without using an organic solvent, which comprises reacting a H3PO4 ester of 2-hydroxyethyl (meth)acrylate having the above formula (II) with the Cu acetate monohydrate having the above formula (III) in water. The complex (I) can be obtained after evaporating water and the resulting acetic acid. The synthesis method of the present invention does not use an organic solvent, and thus does not have drawbacks caused by the organic solvent.
Preferably, a mixture of H3PO4 mono- and di-ester of 2-hydroxyethyl (meth)acrylate with n=1 and n=2 in the formula (II) is reacted with the Cu acetate monohydrate (III) to form a mixture of complex compounds with n=1 and n=2 in the formula (I). In one of the preferred embodiments of the present invention said mixture of H3PO4 mono- and di-ester of 2-hydroxyethyl (meth)acrylate having a molar ratio of the H3PO4 di-ester of 2-hydroxyethyl (meth)acrylate, n=1, to the H3PO4 mono-ester of 2-hydroxyethyl (meth)acrylate, n=2, is about 0.4.
A suitable amount of the Cu acetate monohydrate (III) used in said reaction is 1%-1000%, preferably 40-90%, based on mole of the H3PO4 ester (II). Preferably, an excess amount of the H3PO4 ester (II) is used in said reaction.
A suitable amount of water used in said reaction is 0.5-100, preferably 3-4, times of weight of said H3PO4 ester (II).
Said reaction of the present invention may be carried out at a temperature between 0-100xc2x0 C. and preferably about 25-60xc2x0 C.